1. Field of the Invention
The present invention relates to methods and apparatus for drilling wells. More particularly, the present invention relates to a rotary steerable drilling system that can be connected directly to a rotary drill string so as to allow for selective control of the direction of drilling within a well bore.
2. Description of Related Art
An oil or gas well often has a subsurface section that is drilled directionally, i.e., inclined at an angle with respect to the vertical and with the inclination having a particular compass heading or azimuth. Although wells having deviated sections may be drilled at any desired location, such as for xe2x80x9chorizontalxe2x80x9d borehole orientation or deviated branch bores from a primary borehole, for example, a significant number of deviated wells are drilled in the marine environment. In such case, a number of deviated wells are drilled from a single offshore production platform in a manner such that the bottoms of the boreholes are distributed over a large area of a producing horizon over which the platform is typically centrally located and wellheads for each of the wells are located on the platform structure.
Whether well drilling is being done on land or in a marine environment, there exists a present need in well drilling activities for extended reach drilling.
A typical procedure for drilling a directional borehole is to remove the drill string and drill bit by which the initial, vertical section of the well was drilled using conventional rotary drilling techniques, and run in at the lower end of the drill string a mud motor having a bent housing which drives the bit in response to circulation of drilling fluid. The bent housing provides a bend angle such that the axis below the bend point, which corresponds to the rotation axis of the bit, has a xe2x80x9ctoolfacexe2x80x9d angle with respect to a reference, as viewed from above. The toolface angle, or simply xe2x80x9ctoolfacexe2x80x9d, establishes the azimuth or compass heading at which the deviated borehole section will be drilled as the mud motor is operated. After the toolface has been established by slowly rotating the drill string and observing the output of various orientation devices, the mud motor and drill bit are lowered, with the drill string non-rotatable to maintain the selected toolface, and the drilling fluid pumps, xe2x80x9cmud pumpsxe2x80x9d, are energized to develop fluid flow through the drill string and mud motor, thereby imparting rotary motion to the mud motor output shaft and the drill bit that is fixed thereto. The presence of the bend angle causes the bit to drill on a curve until a desired borehole inclination has been established. To drill. a borehole section along the desired inclination and azimuth, the drill string is then rotated so that its rotation is superimposed over that of the mud motor output shaft, which causes the bend section to merely orbit around the axis of the borehole so that the drill bit drills straight ahead at whatever inclination and azimuth have been established. If desired, the same directional drilling techniques can be used to curve the wellbore to horizontal and then extend it horizontally into or through the production zone. Measurement-while-drilling xe2x80x9cMWDxe2x80x9d systems commonly are included in the drill string above the mud motor to monitor the progress of the borehole being drilled so that corrective measures can be instituted if the various borehole parameters indicate variance from the projected plan.
Various problems can arise when sections of the well are being drilled with the drill string non-rotatable and with a mud motor being operated by drilling fluid flow. The reactive torque caused by operation of a mud motor can cause the toolface to gradually change so that the borehole is not being deepened at the desired azimuth. If not corrected, the wellbore may extend to a point that is too close to another wellbore, the wellbore may miss the desired xe2x80x9csubsurface targetxe2x80x9d, or the wellbore may simply be of excessive length due to xe2x80x9cwanderingxe2x80x9d. These undesirable factors can cause the drilling costs of the wellbore to be excessive and can decrease the drainage efficiency of fluid production from a subsurface formation of interest. Moreover, a non-rotating drill string may cause increased frictional drag so that there is less control over the xe2x80x9cweight on bitxe2x80x9d and the rate of drill bit penetration can decrease, which can result in substantially increased drilling costs. Of course, a non-rotating drill string is more likely to get stuck in the wellbore than a rotating one, particularly where the drill string extends through a permeable zone that causes significant build up of mud cake on the borehole wall.
In the past, various U.S. patents have issued relative to such rotary steering systems for directional drilling. For example, U.S. Pat. No. 6,092,610, issued on Jul. 25, 2000 to Kosmala et al., describes an actively controlled rotary steerable drilling system having a tool collar rotated by a drill string during well drilling. A bit shaft has an upper portion within the tool collar and a lower end extending from the collar and supporting a drill bit. The bit shaft is omni-directionally pivotally supported intermediate of its upper and lower ends by a universal joint within the collar and is rotatably driven by the collar. To achieve controlled steering of the rotating drill bit, orientation of the bit shaft relative to the tool collar is sensed and the bit shaft is maintained geostationary and selectively axially inclined relative to the tool collar during drill string rotation by rotating it about the universal joint by an offsetting mandrel that is rotated counter to collar rotation and at the same frequency of rotation.
U.S. Pat. No. 6,109,372, issued on Aug. 29, 2000, to Dorel et al., describes another rotary steerable drilling system having a tubular rotary tool collar having rotatably mounted thereabout a substantially non-rotatable sliding sleeve incorporating a plurality of elastic coupling members to maintain the sliding sleeve in coupled rotation with the borehole wall during drilling. An offsetting mandrel is supported within the tool collar by a knuckle joint for pivotable movement and is rotatably driven by the tool collar and has a lower end extending from the collar and adapted to support a drill bit. To achieve controlled steering of the rotating drill bit, orientation of the drilling tool is sensed by navigation sensors and the offsetting mandrel is maintained geostationary and selectively axially inclined relative to the tool collar by orienting it about the knuckle joint responsive to navigation sensors.
U.S. Pat. No. 5,131,479, issued on Jul. 21, 1992 to Boulet et al., describes a rotary drilling device including a means for adjusting the azimuth angle of the path of the drilling tool. The means for adjusting the azimuth angle includes a tubular body having a radially projecting bearing blade and mounted rotatably on the set of rods. A remotely actuable junction makes it possible to fix the set of rods and the tubular body relative to one another in terms of rotation in its active position. In the inactive position of the junction means, the set of rods is freely rotatable within the tubular body which is held immobile in terms of rotation in the drill hole by means of the bearing blade. The bearing blade is placed in the drill hole in an angular orientation making it possible to adjust the azimuth angle in the desired direction.
It is an object of the present invention to provide a rotary steering tool which facilitates directional drilling.
It is another object of the present invention to provide a rotary steering tool which allows the use of mudflow to allow for adjustment of the desired angle of directional drilling.
It is a further object of the present invention to provide a rotary steering tool system which is able to replace conventional mud-motors.
It is a further object of the present invention to provide a rotary steering tool which allows the rotary action of the drill string to drive the bit.
It is a further object of the present invention to provide a rotary steering tool which is relatively inexpensive in comparison with other steering tools.
It is a further object of the present invention to provide a rotary steering tool which reduces xe2x80x9clost-in-holexe2x80x9d risks.
It is a further object of the present invention to provide a rotary steering tool which is relatively small in size and compact for easy transportation.
It is a further object of the present invention to provide a rotary steering tool which reduces rig time with fewer trips out of the hole.
It is a further object of the present invention to provide a rotary steering tool which provides the ability to locate critical measurement devices close to the bit so as to identify pay zones prior to drilling through the zone.
It is still a further object of the present invention to provide a rotary steering tool which allows for the ability to drill with the casing since the rotary steering tool and the drill bit can remain down hole.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
The present invention is a rotary steering apparatus comprising a main body having an interior passageway extending longitudinally therethrough, a sleeve extending around the main body such that the main body is rotatable within the sleeve, and a locking member affixed to the main body. The sleeve has at least one protruding pad extending outwardly of an exterior surface thereof. The locking member is engageable with the sleeve relative to a flow rate of mud through the interior passageway of the main body such that the sleeve is fixed relative to the main body. The main body has a drill string connection at a top end thereof and a drill bit connection at a bottom end thereof. The drill string is connected to the top end of the main body. The drill bit is connected to the opposite end of the main body. The drill string is drivingly connected to the main body so as to rotate the main body so as to drive the drill bit. The sleeve has an interior opening. The main body extends through this interior opening. The sleeve has a hole formed therein opening toward the interior opening. The locking member is engageable with this hole. The hole is radially aligned with the protruding pad. The sleeve has three protruding pads formed on an exterior surface thereof. Each of the protruding pads is evenly spaced from an adjacent protruding pad. In particular, one of the three protruding pads extends outwardly further from the exterior surface than the other of the protruding pads. The hole is aligned with the largest of the protruding pads.
The locking member comprises a flipper member extending pivotally into the interior passageway, a spring connected to the flipper so as to resiliently urge the flipper into the interior passageway, and a rod connected to the flipper so as to move in correspondence with a pivotable movement of the flipper. The rod is engageable with the sleeve so as to fix the sleeve to the main body such that the sleeve rotates correspondingly with a rotation of the main body. The main body has a channel extending transverse to the longitudinal passageway and opens thereto. This sleeve has a hole formed therein which faces the main body. The rod is movable so as to engage the hole. A retaining housing is affixed within the channel. The flipper is pivotally connected to the retaining housing. The spring is positioned within the retaining housing. The rod extends through the retaining housing so as to have an end facing the sleeve. The rod has a diameter less than a diameter of the hole. The flipper urges the rod outwardly of the retaining housing so as to enter the hole. The spring has a predetermined spring rate. The flipper is interactive with the spring such that a desired mudflow rate causes the flipper to overcome the spring rate so as to urge the rod outwardly of the main body.